Black-eyed susan. This tough wildflower (Rudbeckia hirta) is a no-brainer for sowing from seed. Although the black-eyed susan is a biennial or short-lived perennial and is treated as an annual in many areas, it self-seeds freely, so you can get an enduring patch going with little trouble. Sun-loving and drought-tolerant, black-eyed susan is very low-maintenance. Sow in spring or fall; germination typically occurs in one to three weeks, depending on soil temperature and moisture. The first year, flowering is sparse, but the second year's blooms will be robust and abundant.